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Sound class-8
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- 2. PRODUCTIONOFSOUNDWAVES Sound is aform of energy which travels in the form of waves. It produces hearing sensation in our ears. To produce sound we are to make vibrations in a body. For example: Place a bowl upper side down and strike it with spoon. The bowl start vibrating produces particular sound that can be heard.
- 6. When prongs oftuning fork are made to strike with a rubber pad then these begin to vibrate and sound waves are produced which spread all around. Sound waves need a material medium such as solids, liquids and gases for their propagation. Most sound waves reaching our ear have travelled through air. Sound can not travel through a vacuum.
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- 8. The vibrating bodyproduces sound waves. These waves are “longitudinal” waves in nature. The molecules of medium vibrate, due to sound waves along the direction of propagation of sound waves. These are also called compressional waves. Propagation of sound waves produced by vibrating tuning fork.
- 9. When the rightprong of tuning fork moves from mean position ‘O’ to ‘B’ it exerts some pressure on the adjacent layer of air molecules and produces a compression. A moment later, the prong begins to move from ‘B’ to ‘A’. The pressure in the adjacent layer decreases and refraction is produced. This rarefaction is transferred to the air layer next to it and so on.
- 10. As the tuningfork moves back and forth rapidly, a series of compression and rarefaction are created in the air . In this way sound waves propagates through the air.
- 11. Pitch:- Pitch isthe characteristic of sound by which we can distinguish between a shrill and a grave sound.
- 13. The pitch ofsound depends upon the frequency of sound. Greater value of frequency, larger is the value of pitch of sound.
- 14. The frequency ofladies and children is greater than that of men, so voice of ladies and children is shrill and of high pitch. Where as the sound of men is grave due to low pitch. The both pitch and frequency have same unit that is hertz.
- 16. Loudness isthe characteristic of sound by which loud and faint sounds can be distinguished. When we talk to our friends, our voice is low, but when we address a public gathering our voice is loud. Loudness of a sound depends upon following factors.
- 17. Amplitude ofthe vibrating body The loudness of the sound varies directly with the amplitude of the vibrating body. The sound produced by the sitar will be loud if we pluck its wires more violently. Similarly, when we beat a drum forcefully, the amplitude of its membrane increases and we hear a loud sound.
- 18. Area ofthe vibrating body The loudness of the sound depends upon the area of the vibrating body. For example, sound produced by a large drum is louder than that by small one because of its large vibrating area. We can conclude that the loudness increases with the area of the vibrating body.
- 19. Distance fromthe vibrating body Loudness of sound also depends upon the distance of the vibrating body from the listener. It is caused by the decrease in amplitude due to increase in distance. Loudness also depends upon the physical condition of the ears of the listener.
- 20. LOUDNESS Loudness is thecharacteristic of sound by which loud and faint sounds can be distinguished. The magnitude of auditory sensation is called loudness.
- 22. Qualityofsound The characteristic ofsound by which two sounds of same intensity and of same pitch can be distinguished is called quality of sound. We can easily distinguish between the sound of flute and piano. It is due to different quality of these two sounds. We recognize the voice of relative/friend over the cell phone by quality.
- 24. Acoustic Protection The techniqueor method used to absorbed undesirable sounds by soft and porous surfaces is called acoustic protection.
- 25. Noise barriers, madeup of modular panels, provide a more efficient sound block than other sound reduction materials such as concrete, metal or wood.
- 27. Reflection of soundis more prominent if the surface is rigid and smooth, and less if the surface is soft and irregular. Soft materials absorb large amount of sound energy. By using such materials in noisy places we can reduce the level of noise pollution. If the surface of classrooms are too absorbent, the sound level may be low for the audience.
- 28. Sometimes, when soundreflects from the walls, ceiling and floor of a room, the reflecting surfaces are too reflective and the sound becomes garbled due to multiple reflections.
- 29. noiseisnuisance We perceive soundas noise or music. Unpleasant sound is called noise and pleasant sound is called music.
- 31. Noise is unwantedsound that can greatly affect your quality of life and health if continually exposed to it. It can also result in headaches, sleep deprivation and stress, among others. Everyone has a different tolerance threshold when it comes to noise but it is unrealistic to expect complete silence.
- 32. There are manytypes of noise that we can easily avoid or reduce: home entertainment equipment and loud music parties noise from the neighbors noisy animals/ barking dogs Do-It-Yourself work and domestic appliances car and house alarms noise from refrigerated units in shops ventilation fans local pubs and entertainment
- 33. The loud soundof radio television, slamming of door, rumbling of truck, road traffic and sound from neighbor is a noise pollution that can be reduced to some extent and some measure should be taken in this regard to save ourselves from this pollution which is unpleasant disagreeable and headache.
- 34. reflectionofsoundmayproduceecho Hard surfaces suchas walls will reflect sound which we hear a short time after the original sound is called echo.
- 35. Echo can beused to calculate the speed of sound let one is standing at a distance of 100 m from a high wall and clap two wooden block to gather at a such rate that each clap coincide with the echo of the one before calculating the time for one echo we can determine the velocity of sound. V = 2d/t
- 36. Audibility The word “audibility”comes from the word “audible” which means ‘can be heard’. The range of frequencies which a listener can hear is known as the range of audibility.
- 38. Audible frequency range Therange of frequencies which person can hear is called audible frequency range.
- 39. A normal humanear can hear a sound only if its frequency lies between 20Hz and 20,000Hz. In other words, a human ear neither hears a sound of frequency less than 20Hz nor a sound of frequency less than 20,000 Hz. Different peoples have different range of audibility.
- 40. useofultrasound Ultrasound is an oscillatingsound pressure wave with a frequency greater than the upper limit of the human hearing range. Sound waves with frequency above 2000Hz are called ultrasonic waves cannot be heard but can be detected electronically and displaced on cathode ray oscilloscope.
- 42. Usesofultrasound They are usedto detect objects. They are used to measure distances. They are used to Ultrasonic imaging. They are used to veterinary medicine. They are used to human medicine. They are used to cleaning of chemicals. They are used to mixing of chemicals. They are used to accelerate chemical processes. They are used to monitor health and some time to determine the position of unborn baby.
- 43. Ultrasound can alsobe used in ultrasonic drill to cut holes in hard mated rails such as glass steel and jeweler. Ultrasound pluses are being used to distinguish minor tumors and kindly stones. In medical ultrasound is preferred over x - rays as it is less hazardous due to its low energy.